I have been on here awhile now and I have a question.
What is the difference between a 2N or 4N? Is there other numbers, 3 or 5 or 10? Other letters? Does the N stand for something? Who decides if it is a 4N or whatever? Thank you in advance....Jean

Jean:
I will be glad to share what I know about the #(N)'s designation. Most plants are by nature, 2(N) - often referred to as diploid; this means that their DNA is composed of 2 strands. Some plants will naturally mutate into 4(N) strains, referred to as tetraploid; this means that their DNA is composed of 4 strands. This somewhat 'doubles' the DNA's effect on the plant - often making it more vigorous, with larger, more substantial flowers. This is really obvious in Daylilies as the "old-fashioned" diploid strains are rather small and have petals that are similar to tissue-paper; tetraploid daylilies often have HUGE flowers that are very thick petaled and the plants often grow very lush and strong.
Tetraploid plants can be achieved by breeding 4(N) X 4(N) or treating the seeds with strong mutagenic chemicals such as Ethyl methanesulfonate (EMS) or Dimethyl Sulfanate; radiation can also be used. Many of our crop plants, such as corn, have been mutagenically modified to increase crop yields, disease resistance and drought resistance.
Now, about the odd numbered (N)s. When you breed a 2(N) with a 4(N), you get a 3(N), referred to as a triploid or a "craploid"; they are often weak, sterile and seldom achieve high standards. But as in all things, there are exceptions. I recently ran across and Ad for a 3(N) SLC that was beautiful and EXPENSIVE. As someone looking for superior breed stock, it held no interest for me as it could be sterile or would throw inferior plants; but, this plant was obviously throwing it's strongest traits out and was, again, a beautiful example.
Are there 5(N), 6(N), etc? Rule out nothing in the plant world. It is my understanding that as long as the (N) is even numbered, most of the progeny should be outstanding. But if there is an odd DNA strand, resulting in an odd (N) number, the results are unstable.
Now - the unspoken questions - How do you know the (N) of a plant? It can be detected using proper lab equipment, but when purchasing, unless you have a portable lab, you have to just trust the seller to be honest with you about it. You can look at the breeding, and as long as the parents were 4(N), you should have a 4(N) plant - but again, unless you can check the DNA strands or the seller offers some proof that such a test was run on the parents, you just have to trust their word. Sometimes the plant will look amazingly stronger, larger bloomed, better substance, etc, but looks can never be trusted to determine DNA. It is a shame that there is not documentation provided for all 4(N) lines as they are often sold for considerably more than their 2(N) relatives. I have seen 10X price increase in one case - BLC. Ports of Paradise 4(N) - approx. $30.00 for a 2(N) division - $300.00 for a 4(N) division.
Does that help? If others have more to add or if I have represented something incorrectly, please provide input / correction. I would appreciate it.
Have a great day -
Steve

Thank you Steve, I should have figured that it was something scientific rather than an arbitrary decision made by who knows who. So I guess that it would be preferable to have a 4N for the beauty of it but almost a necessity if you were breeding them.Thanks for the info...I hated not knowing what everyone was talking about...Jean

If you want to check if your plant is a diploid or quadriploid you can call a local university and speak to the cell biology department. All you have to do is ask if a student would be willing to do a chromosome count on some of your plants. It's simple and they will more than likely oblige.

ZWUM:
Great Idea! I had not thought of that, but I would imagine that students would find this both interesting and educational! I wish I had thought of that!!!
VJO:
Yes, the 4(N) is good for breeding as long as you have another 4(N) to breed with, but 4(N) is somewhat rare to find. Almost all crosses are still made with 2(N) - 4(N) orchids are still sort of the odd-balls of the orc world. Often they are too expensive to make it into the commercial sales and overall they are hard to locate in the orchid world. You can find them, but be ready to search long and pay dearly.
I am glad so many people are able to enjoy this thread. Thanks for asking VJO!
Steve

ZWUM, would there be any reason for me to do that if I wasn't going to sell or breed them? Is it something everyone should know about their orchids? I have a good friend that is the head of the ag department at College of the Ozarks,he probably has it done all the time. Will see what he says
Thank you for the info.....Jean